Heteroatom-enhanced dual-ion storage of a thiophene-based bipyridine polymer for high-capacity and high-rate lithium-ion batteries

Abstract

Organic electrodes are promising next-generation materials owing to their resource abundance and tunable redox properties, yet their practical use is limited by solubility in organic electrolytes, low conductivity, and “dead mass” issues. This study addresses these challenges through a novel 2,2′-dithiophene-linked bipyridine polymer (P-DTBPY) synthesized via in situ electropolymerization. The polymer integrated p-type 2,2′-dithiophene and n-type bipyridine units, enabling efficient dual-ion storage for high-energy/power performance. The 2,2′-dithiophene linkers served dual roles as electropolymerization sites/p-type active centers and conjugation extenders along the polymer backbone, thereby enhancing electronic conductivity and rate capability. This molecular design effectively minimized inactive “dead masses” while maximizing redox activity. The optimized electrode delivered a specific capacity of 260 mAh g⁻¹ at 0.1 A g⁻¹, retained 93.6% capacity after 2000 cycles at 5 A g⁻¹, and achieved 110 mAh g⁻¹ at 10 A g⁻¹. A series of material characterizations, including Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis, along with theoretical calculations, elucidated the dual-ion storage mechanism. These findings provide valuable insights into the design and synthesis of novel electropolymerized bipolar electrodes, paving the way for the development of high-performance dual-ion batteries.